Introducing Data Structures and Algorithms

8/6/2019 Introducing Data Structures and Algorithms

1/23

Ateneo de Naga University

Welcome toCOEM3111st Semester, S/Y 2011-2012

Robert John F. Buena, CpEinstructor


2/23

Data

Structuresand

Algorithms


3/23

Overview of DataStructures and Algorithms


4/23

Obj ectivesFind out why you need to knowabout data structures and

algorithmsDiscover what data structures andalgorithms areLearn some terminology well usein the rest of the book


5/23

W hat is a data structure?an arrangement of data in acomputers memory (or sometimes on a disk)include linked lists, stacks,binary trees, and hash ta bles,among others


6/23

W hat is an algorithm?detailed instructions for carrying out some operationmanipulates the data in thosestructures in various ways,such as inserting a new dataitem, searching for aparticular item, or sorting theitems


7/23

Some Uses for DataStructures and Algorithms

Real-world Data StorageProgrammers ToolModeling


8/23

Real-world Data Storagedata that descri bes physicalentities external to the computer e.g personnel record, inventoryrecord, financial transaction

recordCard file program (simulates abox of index cards)


9/23

Q uestions to answer inwriting a card file program

y How would you store the data in your computers memory?

y

W ould your method work for a hundred filecards? A thousand? A million?y W ould your method permit quick insertion of

new cards and deletion of old ones?y W

ould it allow for fast searching for a specifiedcard?y Suppose you wanted to arrange the cards in

alpha betical order. How would you sort them?


10/23

Programmers Toolsome data storage structures arenot meant to be accessed by the

user, but by the program itself programmer uses suchstructures as tools to facilitatesome other operationstacks, queues, and priorityqueues are often used in thisway


11/23

Real-world Modelingsome data structures directlymodel a real-world situationstacks, queues, and priorityqueues are often used for thispurpose

a queue, for example, can modelcustomers waiting in line at abank


12/23

Overview of Data StructuresData Structure Advantages Disadvantages

Array Q uick insertion, veryfast access if index known. Slow search, slow deletion, fixed

size.Ordered array Q uicker search than

unsorted array. Slow insertion and deletion, fixed size.Stack Provides last-in,

first-out access. Slow access to other items.

Q ueue Provides first-in,first-out access. Slow access to other items.

Linked list Q uick insertion, quickdeletion. Slow search.

Binary tree Q uick search, insertion,deletion (if treeremains balanced). Deletion algorithm is

complex.Red- black tree Q uick search, insertion,

deletion. Tree alwaysbalanced. Complex.


13/23

Overview of Data StructuresData Structure Advantages Disadvantages2-3-4 tree Q uick search, insertion,

deletion. Tree alwaysbalanced. Similar treesgood for disk storage. Complex.

Hash ta ble Very fast access if keyknown. Fast insertion. Slow deletion, accessslow if key not known,inefficient memory usage.

Heap Fast insertion,deletion,access to largest item. Slow access to other items


14/23

Overview of AlgorithmsInsert a new data itemSearch for a specified itemDelete a specified itemtraverse - visiting each item in turn

sorting - ordered arrangement of items based on a keyrecursion - function calling itself


15/23

Initial Definitionsdata filerecordsfieldskeysearch key


16/23

Data filea collection of similar data itemse.g. if you create an address book using

the Card file program, the collection of cards youve created constitutes a datafile.the word f ile should not be confused with

the files stored on a computers hard disk.a data file refers to data in the real world,which might or might not be associatedwith a computer.


17/23

RecordR ecords are the units into which a data file isdivided.They provide a format for storing information.

In the Card file program, each card representsa record.A record includes all the information a boutsome entity, in a situation in which there are

many such entities.A record might correspond to a person in apersonnel file, a car part in an auto supplyinventory, or a recipe in a cook book file.


18/23

FieldsA record is usually dividedinto several f ieldsA field holds a particular kindof dataMore sophisticated data baseprograms use records withmore fields than Card file has


19/23

Key

To search for a record withina data file you must designateone of the records fields as ak ey key unloc k s the entire record


20/23


21/23

Summaryy A data structure is the organization of data in acomputers memory (or in a disk file).

y The correct choice of data structure allows ma jor

improvements in program efficiency.y Examples of data structures are arrays, stacks,

and linked lists.y An algorithm is a procedure for carrying out a

particular task.y Data structures can be used to build data files.y A data file is a collection of many similar records.y Examples of data files are address books, recipe

books, and inventory records.


22/23

Summaryy Data structures can also be used as

programmers tools: they help execute analgorithm.

y A record often represents a real-world o bject, likean employee or a car part.

y A record is divided into fields. Each field storesone characteristic of the o bject descri bed by therecord.

y A key is a field thats used to carry out some

operation on the data. For example, personnelrecords might be sorted by a LastName field.y A datafile can be searched for all records whose

key field has a certain value. This value is calleda search key.


23/23

Workshop

1. W hat is a data structure?2. W hat is an algorithm?

3. Name two things you can use datastructures for.

4. Name an algorithm commonly applied tostored data.

5. True or false: There is only one record in adata file.

Introducing Data Structures and Algorithms

Documents